Introduce OnceClosure and BindOnce

base/bind_unittest.cc

Index: base/bind_unittest.cc
diff --git a/base/bind_unittest.cc b/base/bind_unittest.cc
index 1e3540bf7e7019623af97f931a8cc870891f725d..68a18996c00959ff80ac235523cfe1d6e4872351 100644
--- a/base/bind_unittest.cc
+++ b/base/bind_unittest.cc
@@ -1069,6 +1069,80 @@ TEST_F(BindTest, CapturelessLambda) {
   EXPECT_EQ(42, x);
 }
 
+TEST_F(BindTest, OneShotCallback) {
+  using internal::RepeatingClosure;
+  using internal::OneShotClosure;
+  using internal::BindOneShot;
+  using internal::BindRepeating;
+  using internal::OneShotCallback;
+
+  // Check if Callback variants have declarations of conversions as expected.
+  // Copy constructor and assignment of RepeatingCallback.
+  EXPECT_TRUE((std::is_constructible<
+      RepeatingClosure, const RepeatingClosure&>::value));
+  EXPECT_TRUE((is_assignable<
+      RepeatingClosure, const RepeatingClosure&>::value));
+
+  // Move constructor and assignment of RepeatingCallback.
+  EXPECT_TRUE((std::is_constructible<
+      RepeatingClosure, RepeatingClosure&&>::value));
+  EXPECT_TRUE((is_assignable<
+      RepeatingClosure, RepeatingClosure&&>::value));
+
+  // Conversions from OneShotCallback to RepeatingCallback.
+  EXPECT_FALSE((std::is_constructible<
+      RepeatingClosure, const OneShotClosure&>::value));
+  EXPECT_FALSE((is_assignable<
+      RepeatingClosure, const OneShotClosure&>::value));
+
+  // Destructive conversions from OneShotCallback to RepeatingCallback.
+  EXPECT_FALSE((std::is_constructible<
+      RepeatingClosure, OneShotClosure&&>::value));
+  EXPECT_FALSE((is_assignable<
+      RepeatingClosure, OneShotClosure&&>::value));
+
+  // Copy constructor and assignment of OneShotCallback.
+  EXPECT_FALSE((std::is_constructible<
+      OneShotClosure, const OneShotClosure&>::value));
+  EXPECT_FALSE((is_assignable<
+      OneShotClosure, const OneShotClosure&>::value));
+
+  // Move constructor and assignment of OneShotCallback.
+  EXPECT_TRUE((std::is_constructible<
+      OneShotClosure, OneShotClosure&&>::value));
+  EXPECT_TRUE((is_assignable<
+      OneShotClosure, OneShotClosure&&>::value));
+
+  // Conversions from RepeatingCallback to OneShotCallback.
+  EXPECT_TRUE((std::is_constructible<
+      OneShotClosure, const RepeatingClosure&>::value));
+  EXPECT_TRUE((is_assignable<
+      OneShotClosure, const RepeatingClosure&>::value));
+
+  // Destructive conversions from RepeatingCallback to OneShotCallback.
+  EXPECT_TRUE((std::is_constructible<
+      OneShotClosure, RepeatingClosure&&>::value));
+  EXPECT_TRUE((is_assignable<
+      OneShotClosure, RepeatingClosure&&>::value));
+
+  OneShotClosure cb = BindOneShot(&VoidPolymorphic<>::Run);
+  std::move(cb).Run();
+
+  // RepeatingCallback should be convertible to OneShotCallback.
+  OneShotClosure cb2 = BindRepeating(&VoidPolymorphic<>::Run);
+  std::move(cb2).Run();
+
+  RepeatingClosure cb3 = BindRepeating(&VoidPolymorphic<>::Run);
+  cb = cb3;
+  std::move(cb).Run();
+
+  cb = std::move(cb2);
+
+  OneShotCallback<void(int)> cb4 = BindOneShot(
+      &VoidPolymorphic<std::unique_ptr<int>, int>::Run, MakeUnique<int>(0));
+  BindOneShot(std::move(cb4), 1).Run();
+}
+
 // Callback construction and assignment tests.
 //   - Construction from an InvokerStorageHolder should not cause ref/deref.
 //   - Assignment from other callback should only cause one ref